Ayman al-Zawahri speaks in a video from an undisclosed location in 2012. / AFP/Getty Images

by Melanie Eversley, USA TODAY

by Melanie Eversley, USA TODAY

An al-Qaeda leader is calling on Muslims to continue attacking Americans in the U.S. in order to attack the economy, the BBC, CBS News and other news organizations are reporting.

"To keep up the hemorrhage in America's security and military spending, we need to keep the United States on a constant state of alert about where and when the next strike will blow," CBS News quoted Ayman al-Zawahri as saying in an hour-plus audio message released on jihadi blogs and produced by al-Qaeda.

The message was released to mark the 12th anniversary of the Sept. 11, 2001, terror attacks on the World Trade Center and the Pentagon, CBS reports.

The recording by Zawahri also hailed the April 15th bombings at the Boston Marathon finish line and stressed the importance of small-scale attacks as part of the terror group's strategy, the BBC reports.

"We must bleed America economically by provoking it, so that it continues its massive expenditures on security," Zawahri said. "America's weak spot is its economy, which began to totter from the drain of its military and security expenditure."

The BBC speculated that the emphasis on smaller-scale strikes might illustrate a diminished ability to carry out attacks of the same magnitude it has planned in the past.

Of the economic boycott, Zawahri said, "We must explain to them that every dollar's worth of goods that we buy from America and her allies amounts to a bullet or shrapnel that kills a Muslim or Palestine or Afghanistan."